Summary
In this article, you’ve seen how you can use the HTTP caching and conditional GET feature of the HTTP protocol to reduce the bandwidth requirements of your server and improve the speed of your web applications. Successful implementation of HTTP caching requires the ability to determine the date/time of last change to your content. This timestamp is computed based on the file-modification timestamp of the current web page, any included libraries, and any external files it might reference.
The HTTP caching model also supports entity tags that you can use to show different content on the same web page to different users, as well as a method to request that browsers recheck the content’s validity each time it’s presented to the end user.